1. Technical Field of the Invention
This invention relates to a plating apparatus and a plating method. More particularly, the invention relates to a plating apparatus and a plating method used to fill fine recesses for interconnections formed on a surface of a semiconductor substrate with copper by plating, thereby forming copper interconnections.
2. Description of Related Art
Recently, it has become common practice to use apparatuses for metal plating, such as copper plating, in filling up fine trenches or via holes for interconnections formed on the surface of a substrate such as a semiconductor wafer. Using the apparatuses, the trenches or via holes are filled with plated metal, such as copper with lower electric resistivity than aluminum or aluminum-based materials, thereby forming buried interconnections or the like.
FIG. 13 shows a conventional general constitution of a jet plating apparatus adopting a facedown method among the plating apparatuses of the above-mentioned type. This plating apparatus comprises a cylindrical plating bath 112 opening upward and holding a plating liquid 10 therein, and a head portion 114 for detachably holding a substrate W, such as a semiconductor wafer, so as to face downward, and disposing the substrate W at a position at which it closes the upper opened end of the plating bath 112. A flat plate-shaped anode plate 116 immersed in the plating liquid 10 to serve as an anode is horizontally placed inside the plating bath 112, and the surface (the surface to be plated) of the substrate W is designed to serve as a cathode. The anode plate 116 is made of a porous material or a mesh-like material.
A plating liquid ejection pipe 118 for forming an upward flow of a plating liquid is connected to the center of the bottom in the plating bath 112. A plating liquid reservoir 120 is placed outside an upper portion of the plating bath 112. The plating liquid ejection pipe 118 is connected to a plating liquid supply pipe 128 extending from a plating liquid storage tank 122 and having a pump 124 and a filter 126 installed in the interior thereof. The plating liquid storage tank 122 is connected to a plating liquid return pipe 130 extending from the plating liquid reservoir 120.
According to this structure, the substrate W is held in such a state that the surface of the substrate W face downwardly at the top of the plating bath 112 by the head portion 114. With a certain voltage being applied between the anode plate 116 (anode) and the surface of the substrate W (cathode), the plating liquid 10 inside the plating liquid storage tank 122 is ejected upwardly from the bottom of the plating bath 112 by the pump 124 to direct a flow of the plating liquid vertically at the lower surface (the surface to be plated) of the substrate W. In this manner, plating current is flowed between the anode plate 116 and the substrate W to form a plated film on the lower surface of the substrate W. At this time, the plating liquid 10, which has overflowed the plating bath 112, is recovered by the plating liquid reservoir 120, and returned to the plating liquid storage tank 122.
With the conventional jet plating apparatus, the substrate is lowered while being held horizontally, whereby the lower surface (the surface to be plated) of the substrate is brought into contact with the liquid surface (overflow surface) of the plating liquid. The substrate is further lowered, until the entire lower surface of the substrate is immersed in the plating liquid. Therefore, when the substrate is immersed in the plating liquid, air bubbles are liable to remain on the lower surface of the substrate. As a result, a normal plated film cannot be formed, and defects, such as a deficiency in the plated film, tend to be produced.